Complement and the Clearance of Staphylococcus aureus

金黄色葡萄球菌的补体和清除

基本信息

批准号：
6869638
负责人：
KENJI Mason CUNNION
金额：
$ 11.64万
依托单位：
EASTERN VIRGINIA MEDICAL SCHOOL
依托单位国家：
美国
项目类别：
财政年份：
2002
资助国家：
美国
起止时间：
2002-04-01 至 2007-03-31
项目状态：
已结题

项目摘要

This research will characterize the role of complement proteins in the immune-mediated opsonophagocytosis and killing of pathogenic Staphylococcus aureus. S. aureus is a leading cause of death from infection in hospitals and is increasingly resistant to current antibiotics. For many bacteria adequate opsonization by complement proteins is critical for effectively preventing and fighting infections. Studying complement-mediated opsonization of S. aureus may provide clues to unlock new therapies against S. aureus. Encapsulated (CP+) strains, serotypes 5 and 8, cause 70% of severe S. aureus infections, however their opsonization by complement remains largely unstudied. Our preliminary in vivo and in vitro studies and in vitro studies have investigated three CP+ strains, two heavily- encapsulated strains, and one capsule-negative mutant in terms of lethality in complemented mice, C3 binding kinetics, pathways of complement activation, the nature of C3 fragments deposited and shed, the relationship between growth and C3 binding, and the effect of capsule on C3 binding. The data from these studies suggest that complement is important for surviving bacteremia with clinically relevant S. aureus serotypes. CP+ strains appear to inhibit opsonization by decreasing C3 binding, inhibiting bound C3-fragment recognition by complement receptors, and sh4edding bound C3-fragments. The global hypothesis guiding this research is that the severity of S. aur5eus infection depends on serotype dependent staphylococcal-capsule modulation of complement-mediated opsonization. In light of the preliminary data the following focused hypotheses will be tested: 1) Opsonization by complement is critical in host defense against S. aureus. 2) Capsular polysaccharide and impairs opsonphagocytosis of S. aureus by interfering with normal complement function. 3) S. aureus protects itself by degrading and shedding the major complement opsonins C3b and iC3b. 4) Anti-capsular antibodies improve the complement-mediated opsonophagocytosis and killing of S. aureus. These experiments will be performed using radiolabeled complement components, and antibodies raised against specific complement peptides. Human neutrophils will be incubated with opsonized bacteria and stained with acridine orange to measure phagocytosis and intracellular killing. In vivo experiments will be performed using complement deficient mice. Collaborating laboratories have provided special S. aureus stains and anti-S. aureus antibodies.

这项研究将表征补体蛋白在免疫介导的调理吞噬作用和杀死致病性金黄色葡萄球菌中的作用。金黄色葡萄球菌是医院感染导致死亡的主要原因，并且对现有抗生素的耐药性越来越强。对于许多细菌来说，补体蛋白的充分调理作用对于有效预防和抵抗感染至关重要。研究金黄色葡萄球菌补体介导的调理作用可能为开发针对金黄色葡萄球菌的新疗法提供线索。有荚膜 (CP+) 菌株（血清型 5 和 8）引起 70% 的严重金黄色葡萄球菌感染，但补体对它们的调理作用仍然很大程度上未经研究。我们的初步体内和体外研究以及体外研究调查了三种 CP+ 菌株、两种重包膜菌株和一种包膜阴性突变体，包括补体小鼠的致死率、C3 结合动力学、补体激活途径、补体的性质。 C3 片段沉积和脱落、生长与 C3 结合之间的关系以及胶囊对 C3 结合的影响。这些研究的数据表明，补体对于临床相关金黄色葡萄球菌血清型的菌血症的存活很重要。 CP+菌株似乎通过减少C3结合、抑制补体受体识别结合的C3片段以及sh4edding结合的C3片段来抑制调理作用。指导这项研究的总体假设是，金黄色葡萄球菌感染的严重程度取决于补体介导的调理作用的血清型依赖性葡萄球菌荚膜调节。根据初步数据，将测试以下重点假设：1）补体的调理作用对于宿主针对金黄色葡萄球菌的防御至关重要。 2) 荚膜多糖，通过干扰正常的补体功能来损害金黄色葡萄球菌的调理吞噬作用。 3) 金黄色葡萄球菌通过降解和脱落主要补体调理素 C3b 和 iC3b 来保护自身。 4) 抗荚膜抗体改善补体介导的调理吞噬作用并杀死金黄色葡萄球菌。这些实验将使用放射性标记的补体成分和针对特定补体肽的抗体进行。人中性粒细胞将与调理细菌一起孵育，并用吖啶橙染色以测量吞噬作用和细胞内杀伤作用。将使用补体缺陷小鼠进行体内实验。合作实验室提供了特殊的金黄色葡萄球菌染色剂和抗金黄色葡萄球菌染色剂。金黄色葡萄球菌抗体。